ROFL - exercise can affect you for up to 48 hours Marie !
You should have left the TBR on for several hours after the walk at least. I can't tell you how long or anything - no idea as we are all different. I'd have reduced my meal bolus by 10% too.
Usually if I were to walk for an hour in the morning, and not go too far or too fast, I'd probably be OK pre bed.
But if I walk in the pm, the TBR and reduced bolus will stay on till bedtime.
You just have to play till you get it right, so it';s important to record all this in your pump diary so you can look see what you did last time and consider if you need to change what you did.